socket: enforce limit on number of concurrent connections

6 files changed, 129 insertions, 25 deletions

diff --git a/src/load-fragment.c b/src/load-fragment.c
index d6a35f7ff0..b7bb4d7c5c 100644
--- a/src/load-fragment.c
+++ b/src/load-fragment.c
@@ -1516,6 +1516,7 @@ static int load_from_path(Unit *u, const char *path) {
                 { "SocketMode",             config_parse_mode,            &u->socket.socket_mode,                          "Socket"  },
                 { "KillMode",               config_parse_kill_mode,       &u->socket.kill_mode,                            "Socket"  },
                 { "Accept",                 config_parse_bool,            &u->socket.accept,                               "Socket"  },
+                { "MaxConnections",         config_parse_unsigned,        &u->socket.max_connections,                      "Socket"  },
                 EXEC_CONTEXT_CONFIG_ITEMS(u->socket.exec_context, "Socket"),
 
                 { "What",                   config_parse_string,          &u->mount.parameters_fragment.what,              "Mount"   },
diff --git a/src/mount.c b/src/mount.c
index c95581fd1e..5c16f86d53 100644
--- a/src/mount.c
+++ b/src/mount.c
@@ -645,7 +645,7 @@ static void mount_enter_unmounting(Mount *m, bool success) {
         return;
 
 fail:
-        log_warning("%s failed to run umount exectuable: %s", UNIT(m)->meta.id, strerror(-r));
+        log_warning("%s failed to run 'umount' task: %s", UNIT(m)->meta.id, strerror(-r));
         mount_enter_mounted(m, false);
 }
 
@@ -688,7 +688,7 @@ static void mount_enter_mounting(Mount *m) {
         return;
 
 fail:
-        log_warning("%s failed to run mount exectuable: %s", UNIT(m)->meta.id, strerror(-r));
+        log_warning("%s failed to run 'mount' task: %s", UNIT(m)->meta.id, strerror(-r));
         mount_enter_dead(m, false);
 }
 
diff --git a/src/service.c b/src/service.c
index b8687b7cf5..4375cb5cb1 100644
--- a/src/service.c
+++ b/src/service.c
@@ -157,6 +157,16 @@ static void service_close_socket_fd(Service *s) {
         s->socket_fd = -1;
 }
 
+static void service_connection_unref(Service *s) {
+        assert(s);
+
+        if (!s->socket)
+                return;
+
+        socket_connection_unref(s->socket);
+        s->socket = NULL;
+}
+
 static void service_done(Unit *u) {
         Service *s = SERVICE(u);
 
@@ -190,6 +200,7 @@ static void service_done(Unit *u) {
         }
 
         service_close_socket_fd(s);
+        service_connection_unref(s);
 
         unit_unwatch_timer(u, &s->timer_watch);
 }
@@ -800,6 +811,11 @@ static int service_verify(Service *s) {
                 return -EINVAL;
         }
 
+        if (s->exec_command[SERVICE_EXEC_START]->command_next) {
+                log_error("%s has more than one ExecStart setting. Refusing.", UNIT(s)->meta.id);
+                return -EINVAL;
+        }
+
         if (s->type == SERVICE_DBUS && !s->bus_name) {
                 log_error("%s is of type D-Bus but no D-Bus service name has been specified. Refusing.", UNIT(s)->meta.id);
                 return -EINVAL;
@@ -993,6 +1009,9 @@ static int service_get_sockets(Service *s, Set **_set) {
         assert(s);
         assert(_set);
 
+        if (s->socket_fd >= 0)
+                return 0;
+
         /* Collects all Socket objects that belong to this
          * service. Note that a service might have multiple sockets
          * via multiple names. */
@@ -1038,6 +1057,9 @@ static int service_notify_sockets_dead(Service *s) {
 
         assert(s);
 
+        if (s->socket_fd >= 0)
+                return 0;
+
         /* Notifies all our sockets when we die */
         if ((r = service_get_sockets(s, &set)) < 0)
                 return r;
@@ -1107,8 +1129,19 @@ static void service_set_state(Service *s, ServiceState state) {
 
         if (state != SERVICE_START_PRE &&
             state != SERVICE_START &&
-            !(state == SERVICE_DEAD && UNIT(s)->meta.job))
+            state != SERVICE_START_POST &&
+            state != SERVICE_RUNNING &&
+            state != SERVICE_RELOAD &&
+            state != SERVICE_STOP &&
+            state != SERVICE_STOP_SIGTERM &&
+            state != SERVICE_STOP_SIGKILL &&
+            state != SERVICE_STOP_POST &&
+            state != SERVICE_FINAL_SIGTERM &&
+            state != SERVICE_FINAL_SIGKILL &&
+            !(state == SERVICE_DEAD && UNIT(s)->meta.job)) {
                 service_close_socket_fd(s);
+                service_connection_unref(s);
+        }
 
         if (old_state != state)
                 log_debug("%s changed %s -> %s", UNIT(s)->meta.id, service_state_to_string(old_state), service_state_to_string(state));
@@ -1194,6 +1227,9 @@ static int service_collect_fds(Service *s, int **fds, unsigned *n_fds) {
         assert(fds);
         assert(n_fds);
 
+        if (s->socket_fd >= 0)
+                return 0;
+
         if ((r = service_get_sockets(s, &set)) < 0)
                 return r;
 
@@ -1255,7 +1291,7 @@ static int service_spawn(
 
         pid_t pid;
         int r;
-        int *fds = NULL;
+        int *fds = NULL, *fdsbuf = NULL;
         unsigned n_fds = 0;
         char **argv = NULL, **env = NULL;
 
@@ -1263,12 +1299,20 @@ static int service_spawn(
         assert(c);
         assert(_pid);
 
-        if (pass_fds) {
+        if (pass_fds ||
+            s->exec_context.std_input == EXEC_INPUT_SOCKET ||
+            s->exec_context.std_output == EXEC_OUTPUT_SOCKET ||
+            s->exec_context.std_error == EXEC_OUTPUT_SOCKET) {
+
                 if (s->socket_fd >= 0) {
                         fds = &s->socket_fd;
                         n_fds = 1;
-                } else if ((r = service_collect_fds(s, &fds, &n_fds)) < 0)
-                        goto fail;
+                } else {
+                        if ((r = service_collect_fds(s, &fdsbuf, &n_fds)) < 0)
+                                goto fail;
+
+                        fds = fdsbuf;
+                }
         }
 
         if (timeout && s->timeout_usec) {
@@ -1321,12 +1365,8 @@ static int service_spawn(
         if (r < 0)
                 goto fail;
 
-        if (fds) {
-                if (s->socket_fd >= 0)
-                        service_close_socket_fd(s);
-                else
-                        free(fds);
-        }
+        if (fdsbuf)
+                free(fdsbuf);
 
         if ((r = unit_watch_pid(UNIT(s), pid)) < 0)
                 /* FIXME: we need to do something here */
@@ -1756,7 +1796,7 @@ static void service_run_next(Service *s, bool success) {
         return;
 
 fail:
-        log_warning("%s failed to run spawn next task: %s", UNIT(s)->meta.id, strerror(-r));
+        log_warning("%s failed to run next task: %s", UNIT(s)->meta.id, strerror(-r));
 
         if (s->state == SERVICE_START_PRE)
                 service_enter_signal(s, SERVICE_FINAL_SIGTERM, false);
@@ -2524,7 +2564,7 @@ static void service_bus_query_pid_done(
                 service_set_main_pid(s, pid);
 }
 
-int service_set_socket_fd(Service *s, int fd) {
+int service_set_socket_fd(Service *s, int fd, Socket *sock) {
         assert(s);
         assert(fd >= 0);
 
@@ -2543,6 +2583,8 @@ int service_set_socket_fd(Service *s, int fd) {
 
         s->socket_fd = fd;
         s->got_socket_fd = true;
+        s->socket = sock;
+
         return 0;
 }
 
diff --git a/src/service.h b/src/service.h
index 7b85771a30..6c1612d0f5 100644
--- a/src/service.h
+++ b/src/service.h
@@ -137,13 +137,14 @@ struct Service {
         RateLimit ratelimit;
 
         int socket_fd;
+        struct Socket *socket;
 
         Watch timer_watch;
 };
 
 extern const UnitVTable service_vtable;
 
-int service_set_socket_fd(Service *s, int fd);
+int service_set_socket_fd(Service *s, int fd, struct Socket *socket);
 
 const char* service_state_to_string(ServiceState i);
 ServiceState service_state_from_string(const char *s);
diff --git a/src/socket.c b/src/socket.c
index 874cc91697..fdb6f66b6f 100644
--- a/src/socket.c
+++ b/src/socket.c
@@ -63,6 +63,8 @@ static void socket_init(Unit *u) {
         s->directory_mode = 0755;
         s->socket_mode = 0666;
 
+        s->max_connections = 64;
+
         exec_context_init(&s->exec_context);
 
         s->control_command_id = _SOCKET_EXEC_COMMAND_INVALID;
@@ -81,6 +83,7 @@ static void socket_unwatch_control_pid(Socket *s) {
 static void socket_done(Unit *u) {
         Socket *s = SOCKET(u);
         SocketPort *p;
+        Meta *i;
 
         assert(s);
 
@@ -108,6 +111,14 @@ static void socket_done(Unit *u) {
         s->bind_to_device = NULL;
 
         unit_unwatch_timer(u, &s->timer_watch);
+
+        /* Make sure no service instance refers to us anymore. */
+        LIST_FOREACH(units_per_type, i, u->meta.manager->units_per_type[UNIT_SERVICE]) {
+                Service *service = (Service *) i;
+
+                if (service->socket == s)
+                        service->socket = NULL;
+        }
 }
 
 static bool have_non_accept_socket(Socket *s) {
@@ -141,6 +152,11 @@ static int socket_verify(Socket *s) {
                 return -EINVAL;
         }
 
+        if (s->accept && s->max_connections <= 0) {
+                log_error("%s's MaxConnection setting too small. Refusing.", UNIT(s)->meta.id);
+                return -EINVAL;
+        }
+
         return 0;
 }
 
@@ -307,8 +323,12 @@ static void socket_dump(Unit *u, FILE *f, const char *prefix) {
 
         if (s->accept)
                 fprintf(f,
-                        "%sAccepted: %u\n",
-                        prefix, s->n_accepted);
+                        "%sAccepted: %u\n"
+                        "%sNConnections: %u\n"
+                        "%sMaxConnections: %u\n",
+                        prefix, s->n_accepted,
+                        prefix, s->n_connections,
+                        prefix, s->max_connections);
 
         LIST_FOREACH(port, p, s->ports) {
 
@@ -734,7 +754,7 @@ static void socket_enter_stop_post(Socket *s, bool success) {
         return;
 
 fail:
-        log_warning("%s failed to run stop-post executable: %s", s->meta.id, strerror(-r));
+        log_warning("%s failed to run 'stop-post' task: %s", s->meta.id, strerror(-r));
         socket_enter_signal(s, SOCKET_FINAL_SIGTERM, false);
 }
 
@@ -809,7 +829,7 @@ static void socket_enter_stop_pre(Socket *s, bool success) {
         return;
 
 fail:
-        log_warning("%s failed to run stop-pre executable: %s", s->meta.id, strerror(-r));
+        log_warning("%s failed to run 'stop-pre' task: %s", s->meta.id, strerror(-r));
         socket_enter_stop_post(s, false);
 }
 
@@ -844,7 +864,7 @@ static void socket_enter_start_post(Socket *s) {
 
         if ((s->control_command = s->exec_command[SOCKET_EXEC_START_POST])) {
                 if ((r = socket_spawn(s, s->control_command, &s->control_pid)) < 0) {
-                        log_warning("%s failed to run start-post executable: %s", s->meta.id, strerror(-r));
+                        log_warning("%s failed to run 'start-post' task: %s", s->meta.id, strerror(-r));
                         goto fail;
                 }
 
@@ -877,7 +897,7 @@ static void socket_enter_start_pre(Socket *s) {
         return;
 
 fail:
-        log_warning("%s failed to run start-pre exectuable: %s", s->meta.id, strerror(-r));
+        log_warning("%s failed to run 'start-pre' task: %s", s->meta.id, strerror(-r));
         socket_enter_dead(s, false);
 }
 
@@ -895,6 +915,12 @@ static void socket_enter_running(Socket *s, int cfd) {
                 Unit *u;
                 char *prefix, *instance, *name;
 
+                if (s->n_connections >= s->max_connections) {
+                        log_warning("Too many incoming connections (%u)", s->n_connections);
+                        close_nointr_nofail(cfd);
+                        return;
+                }
+
                 if ((r = instance_from_socket(cfd, s->n_accepted++, &instance)) < 0)
                         goto fail;
 
@@ -919,11 +945,13 @@ static void socket_enter_running(Socket *s, int cfd) {
                 if (r < 0)
                         goto fail;
 
-                if ((r = service_set_socket_fd(SERVICE(u), cfd)) < 0)
+                if ((r = service_set_socket_fd(SERVICE(u), cfd, s)) < 0)
                         goto fail;
 
                 cfd = -1;
 
+                s->n_connections ++;
+
                 if ((r = manager_add_job(u->meta.manager, JOB_START, u, JOB_REPLACE, true, NULL)) < 0)
                         goto fail;
         }
@@ -958,7 +986,7 @@ static void socket_run_next(Socket *s, bool success) {
         return;
 
 fail:
-        log_warning("%s failed to run spawn next executable: %s", s->meta.id, strerror(-r));
+        log_warning("%s failed to run next task: %s", s->meta.id, strerror(-r));
 
         if (s->state == SOCKET_START_POST)
                 socket_enter_stop_pre(s, false);
@@ -1181,6 +1209,14 @@ static const char *socket_sub_state_to_string(Unit *u) {
         return socket_state_to_string(SOCKET(u)->state);
 }
 
+static bool socket_check_gc(Unit *u) {
+        Socket *s = SOCKET(u);
+
+        assert(u);
+
+        return s->n_connections > 0;
+}
+
 static void socket_fd_event(Unit *u, int fd, uint32_t events, Watch *w) {
         Socket *s = SOCKET(u);
         int cfd = -1;
@@ -1375,7 +1411,10 @@ int socket_collect_fds(Socket *s, int **fds, unsigned *n_fds) {
 void socket_notify_service_dead(Socket *s) {
         assert(s);
 
-        /* The service is dead. Dang. */
+        /* The service is dead. Dang!
+         *
+         * This is strictly for one-instance-for-all-connections
+         * services. */
 
         if (s->state == SOCKET_RUNNING) {
                 log_debug("%s got notified about service death.", s->meta.id);
@@ -1383,6 +1422,20 @@ void socket_notify_service_dead(Socket *s) {
         }
 }
 
+void socket_connection_unref(Socket *s) {
+        assert(s);
+
+        /* The service is dead. Yay!
+         *
+         * This is strictly for one-onstance-per-connection
+         * services. */
+
+        assert(s->n_connections > 0);
+        s->n_connections--;
+
+        log_debug("%s: One connection closed, %u left.", s->meta.id, s->n_connections);
+}
+
 static const char* const socket_state_table[_SOCKET_STATE_MAX] = {
         [SOCKET_DEAD] = "dead",
         [SOCKET_START_PRE] = "start-pre",
@@ -1429,6 +1482,8 @@ const UnitVTable socket_vtable = {
         .active_state = socket_active_state,
         .sub_state_to_string = socket_sub_state_to_string,
 
+        .check_gc = socket_check_gc,
+
         .fd_event = socket_fd_event,
         .sigchld_event = socket_sigchld_event,
         .timer_event = socket_timer_event,
diff --git a/src/socket.h b/src/socket.h
index 5a2cd06d9d..31b3870ef6 100644
--- a/src/socket.h
+++ b/src/socket.h
@@ -103,6 +103,8 @@ struct Socket {
 
         bool accept;
         unsigned n_accepted;
+        unsigned n_connections;
+        unsigned max_connections;
 
         bool failure;
         Watch timer_watch;
@@ -118,6 +120,9 @@ void socket_notify_service_dead(Socket *s);
  * any of the sockets of this socket */
 int socket_add_one_mount_link(Socket *s, Mount *m);
 
+/* Called from the service code when a per-connection service ended */
+void socket_connection_unref(Socket *s);
+
 extern const UnitVTable socket_vtable;
 
 const char* socket_state_to_string(SocketState i);